In the game of football, a key requisite is the accurate positioning of the down marker on the sideline relative to the position of the football on the field of play. Also, equally important is the accurate re-positioning of the football relative to the down marker after an incomplete pass or a disallowed play.
The many attempts in the past to provide a device to accomplish the above noted football locating have not been successful because they were too cumbersome. Devices employing boxes of mirrors, optical lasers, or battery assisted systems have not been acceptable. To date, the location of the down marker or the football is determined by the judgment of the game officials.